Power Converter Dead Time Control via Diode Voltage Drop
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power converter systems face challenges in optimizing dead time settings, leading to excessive losses in freewheeling diodes and the risk of short circuits during switching operations, particularly in inversion mode, due to factors like temperature, parasitic inductances, and component fluctuations.
Innovation Solution
A controlling strategy that dynamically adjusts dead time based on voltage drops across freewheeling diodes, using comparators with hysteresis to determine when current has commutated to the inverse diode, thereby preventing 'hot paths' and minimizing power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dead time is increased to prevent hot paths and ensure reliable switching, then switching safety is improved, but power losses in freewheeling diodes increase
Solution Approach 1:
The patent implements dynamic dead time adjustment by continuously monitoring the voltage at the direct voltage terminal and adapting the dead time duration based on operating conditions such as current direction, magnitude, and temperature. This replaces fixed dead time settings with a dynamic control strategy that optimizes the balance between preventing hot paths and minimizing diode conduction losses.
Solution Approach 2:
The patent changes the dead time parameter based on multiple influencing factors including temperature, parasitic inductances, connection characteristics of the intermediate circuit, switching speed of elements, and phase current level. By adjusting this critical parameter adaptively, the system resolves the contradiction between safety and efficiency.
2Loss of energy
If dead time is decreased to reduce power losses in freewheeling diodes, then energy efficiency is improved, but the risk of hot paths and short circuits increases
Solution Approach 1:
The patent employs feedback mechanisms by continuously monitoring the voltage at the direct voltage terminal and using this information to adjust the dead time setting. The control system evaluates the actual switching state and adapts the dead time in real-time, ensuring that it is long enough to prevent hot paths under critical conditions while being minimized under normal operating conditions to reduce losses.
Solution Approach 2:
The patent takes preliminary action by predicting potential switching conflicts based on monitored parameters such as current direction and magnitude, temperature, and parasitic inductances. The dead time is adjusted in advance based on these predictions, preventing hot paths before they occur while minimizing unnecessary dead time extensions that would increase losses.
3Reliability
If dead time is set for worst-case conditions to ensure reliability, then switching safety is improved, but system cost increases due to oversized switching elements
Solution Approach 1:
The patent uses dynamic dead time adjustment to replace the need for oversized switching elements designed for worst-case static conditions. By adapting dead time to actual operating conditions, the system achieves the same reliability with properly sized, cost-effective switching elements, reducing both component costs and system complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces power losses in freewheeling diodes and prevents short circuits, achieving an optimal balance between power loss reduction and safety, while being economically viable and easily integratable into existing systems.
Implementation Method 1
A signal of a comparator allocated to the diode is waited for. The comparator is allocated to a diode and acquires a voltage drop over this diode.
Implementation Method 2
use of a comparator with a predetermined hysteresis characteristic
Data Source
AI summary
A method for operating a power converter having at least one power converter half-bridge, in which a controllable switching element and a freewheeling diode connected parallel thereto and in the blocking direction are provided respectively between a first direct voltage terminal and an alternating voltage terminal as well as between the alternating voltage terminal and a second direct voltage terminal. The switching elements of the at least one half-bridge are controlled in alternating fashion and in each case interrupted by controlling pauses. The duration of the controlling pauses is set on the basis of a determined voltage drop at at least one of the freewheeling diodes.